Water blown, energy absorbing foams

ABSTRACT

A novel isocyanate reactive mixture is described which allows for the preparation of energy absorbing foams which meet Chrysler specification DC-640. The reactive mixture contains a) a filled polyol, b) a propylene oxide adduct of a mono-, di-, or trialkanolamine and c) a polyoxyalkylene polyamine. Foams prepared from the reactive mixture are also described.

This application is a division of application Ser. No. 08/319,189 filedOct. 6, 1994, now U.S. Pat. No. 5,415,802.

BACKGROUND OF THE INVENTION

Energy absorbing foams based upon urethane chemistry are known in theart. The early literature generally utilized halocarbon blowing agents(see, e.g., U.S. Pat. No. 3,926,866). A significant number of patentshave issued relating to water blown energy absorbing foams based uponpolyols ("filled polyols") prepared by polymerizingstyrene/acrylonitrile monomer mixtures in polyethers (see, e.g., U.S.Pat. Nos. 4,116,893, 4,190,712, 4,212,954, 4,866,102, 5,216,041 and5,232,957). Other patented technology describes the use of relativelylow molecular weight crosslinkers (see, e.g., U.S. Pat. Nos. 4,282,330,5,143.941, and 5,167,884) or the use of various polyols, such asethylene oxide adducts of Mannich condensates (U.S. Pat. No. 4,371,629),alkoxylated toluene diamine (U.S. Pat. No. 4,614,754), or polyolsderived from propylene glycol or ethylene diamine (U.S. Pat. No.5,187,204).

In addition, we are aware of a commercially available system for theproduction of energy absorbing foam consisting of:

a) 30 parts by weight of a dispersion of a polyhydrazo-dicarbonamide ina relatively high molecular hydroxyl-containing material;

b) 25 parts by weight of a 630 OH number adduct of ethylene diamine andpropylene oxide,

c) 30 parts by weight of a 28 OH number adduct of propylene glycol,propylene oxide and ethylene oxide (having a 13% by weight EO tip),

d) 1 part by weight of a silicone surfactant,

e) 6.7 parts by weight of water,

f) 0.1 part by weight of a catalyst for catalyzing the reaction betweenwater and an isocyanate group, and

g) 152 parts of a polymethylene poly(phenyl isocyanate).

While some of the systems noted above have been used commercially, thesearch continues for systems which will produce energy absorbing foamswhich will meet a variety of specifications such as Chryslerspecification DC-640 for knee impact, and which also meet commercialproduction processing requirements of 12 second mold closing, 3 minutedemold and low molding pressure. "Mold closing" is defined as the timefrom the start of the introduction of the foamable reactants into themold until the mold is dosed. "Demold" time is defined as the time fromthe start of the introduction of the foamable reactants into the molduntil the finished part is removed from the mold. "Molding pressure" isdefined as the pressure created in the dosed mold by the reacting andgelling reaction mixture and retained internally by the foam if theclosed cell content is high.

DESCRIPTION OF THE INVENTION

A technology based upon a novel polyol mixture has now been developedwhich allows for the production of energy absorbing foams which meet theabove-noted Chrysler specification and which meet the commercialproduction requirements of 12 second mold closing, 3 minute demold andlow molding pressure.

The novel polyol mixture unexpectedly allows for the use of a wide rangeof water levels to produce molded foams of varying densities--all ofwhich exhibit good dimensional stability and a very uniform type ofenergy absorption. The water level can be adjusted easily to adjust thefoam density and allow the foam to meet the above-noted Chryslerspecification. This novel polyol mixture avoids the use of low molecularweight ethylene diamine based crosslinkers which tend to increase closedcell content and foam pressure. "Foam pressure" is the internal foampressure from the dosed cell content of the foam. Ethylene diamine basedcrosslinkers are so catalytic that they control the reaction and createmore dosed cells and therefore higher foam pressures. At 3 minutedemold, this causes post expansion and foam splitting. The novel mixturealso allows for the production of foams displaying very low foampressures with good moldability.

The present invention is directed to an isocyanate reactive mixture andto a foam produced therefrom. More particularly, the isocyanate reactivemixture of the present invention comprises:

a) from about 25 to about 50% by weight of a filled polyol having an OHnumber of from 25 to 50,

b) from 0 to about 30% by weight (and preferably from about 15 to about30% by weight) of a polyether diol having a hydroxyl functionality of 2and having an OH number of from about 25 to about 75, and wherein atleast 75% of the hydroxyl groups are primary hydroxyl groups,

c) from about 20 to about 70% by weight (and preferably from about 20 toabout 55% by weight) of an adduct of a mono-, di-, or trialkanolamineand propylene oxide, said adduct having a hydroxyl number of from about100 to about 800, and

d) from about 5 to about 20% by weight of a polyoxyalkylene polyaminehaving a molecular weight of from about 2000 to about 5000, andcontaining from 2 to 3 primary amino groups,

wherein the percents by weight are based upon the total weight of theisocyanate reactive mixture and wherein the percents by weight total100%. Component a) is preferably a dispersion of a polyurea and/orpolyhydrazodicarbonamide in a relatively high molecular weight organiccompound containing at least two hydroxyl groups, wherein theconcentration of the polyurea and/or polyhydrazodicarbonamide is from 1to 40% by weight based upon 100 parts by weight of said organiccompound, and wherein said dispersion has an OH number of from 25 to 50.

In addition, the present invention is directed to a water blown, energyabsorbing foam produced by reacting:

A) the above-described isocyanate reactive mixture,

B) a polymethylene poly(phenyl isocyanate) containing from about 40 toabout 85% by weight of methylene bis(phenyl isocyanate) and having anisocyanate group content of from about 20 to about 35% by weight(preferably from about 30 to about 35% by weight, and most preferablyfrom about 31 to about 33% by weight), with the amount of saidisocyanate B) being such that the isocyanate index of the mixture of allthe isocyanate reactive components and said isocyanate is from about 95to about 105, and

C) from about 2 to about 10 parts by weight per 100 parts by weight ofcomponent A) of water, in the presence of

D) from 0 to about 1 part by weight per 100 parts by weight of componentA) of a silicone surfactant,

E) from about 0.05 to about 1.0 part by weight per 100 parts by weightof component A) of an amine compound which will catalyze the reactionbetween water and an isocyanate group.

The novel technology herein yields several unexpected findings inaddition to those noted above. The foams produced herein have high opencell content (typically >95%) and uniform cell structure. Lower pressurein the molded foam is attainable with faster demold times. Finally,foams of uniform energy absorption properties with easy densityadjustments can be produced by merely changing the amount of water used.

The foams of the present invention are directed to a water blown, energyabsorbing foam broadly produced by reacting A) a specified isocyanatereactive mixture, B) a polymethylene poly(phenyl isocyanate), and C)water, in the presence of D) a silicone surfactant, and E) a catalyst.

The isocyanate reactive mixture A) comprises the following specificcomponents: a) a filled polyol having an OH number of from 25 to 50, b)optionally, a polyether diol having a hydroxyl functionality of 2 andhaving an OH number of from about 25 to about 75, and wherein at least75% of the hydroxyl groups are primary hydroxyl groups, c) an adduct ofa mono-, di-, or trialkanolamine and propylene oxide, said adduct havinga hydroxyl number of from about 100 to about 800, and d) apolyoxyalkylene polyamine having a molecular weight of from about 2000to about 5000, and containing from 2 to 3 primary amino groups.

Component A)d) is a polyoxyalkylene polyamine having a molecular weightof from about 2000 to about 5000, and containing from 2 to 3 primaryamine groups. Such polyamines are known in the art. One method forpreparing such amines is the amination of polyhydroxy polyethers (e.g.,polypropylene glycols) by a reaction with ammonia in the presence ofRaney nickel and hydrogen (Belgian Patent 634,741). U.S. Pat. No.3,654,370 discloses the preparation of polyoxyalkylene polyamines byreaction of the corresponding polyol with ammonia and hydrogen in thepresence of a nickel, copper, or chromium catalyst. The preparation ofpolyethers containing amino end groups by the hydrogenation ofcyanoethylated polyoxypropylene ethers is described in German Patent1,193,671. Other methods for the preparation of polyoxyalkylenepolyamines are described in U.S. Pat. Nos. 3,155,728 and 3,236,895 andFrench Patent 1,551,605. Commercially available polyether polyamines aresold by Texaco under the Jeffamine tradename.

Component A)a) is a filled polyol. The term "filled polyol" as usedherein means: i) dispersions of polyureas and/orpolyhydrazodicarbonamides in relatively high molecular weight organiccompounds containing at least two hydroxyl groups, ii) polymer polyolsprepared by polymerizing one or more ethylenically unsaturated monomers,such as styrene and acrylonitrile, in relatively high molecular weightorganic compounds containing at least two hydroxyl groups, and iii)mixtures thereof. These filled polyols are known and can becharacterized as hydroxyl containing compounds which contain highmolecular weight polyadducts, polycondensates or polymers in finelydispersed or dissolved form. Polymer polyols are known. Methods fortheir manufacture are described in U.S. Pat. Nos. 3,383,351, 3,304,273,3,523,093, 3,652,639, 3,823,201, and 4,390,645, all the disclosureswhich are hereby incorporated by reference. The polyurea and/orpolyhydrazo-dicarbonamide dispersions are also known and are prepared byreacting an organic polyisocyanate with polyamines containing primaryand/or secondary amine groups, hydrazines, hydrazides, or a mixturethereof in the presence of relatively high molecular weighthydroxyl-containing materials. These dispersions described in U.S. Pat.No. 4,042,537, 4,089,835, 3,325,421, 4,092,275, 4,093,569, 4,119,613,4,147,680, 4,184,990, 4,293,470, 4,296,213, 4,305,857, 4,305,858,4,310,448, 4,310,449, 4,324,716, 4,374,209, 4,496,678, 4,523,025,4,668,734, 4,761,434, and 4,847,320, all the disclosures which arehereby incorporated by reference. The dispersions typically have solidscontents of from 1 to 40% by weight and preferably from 10 to 30% byweight.

The other polyols used in component A) and their methods of manufactureare generally known in the art. These are produced by the addition ofepoxides (preferably ethylene and/or propylene oxide) either inadmixture or successively, to compounds containing reactive hydrogenatoms. Examples of suitable reactive compounds for components A)b)include propane diol, dipropylene diol, butane diol and the like, whilemono-, di- and trialkanolamines are used to produce component A)c). Inthe case of component A)b), ethylene oxide is utilized to cap the polyolwith the requisite content of primary hydroxyl groups.

The polymethylene poly(phenyl isocyanates) useful herein are known inthe art and are produced by reacting phosgene with aniline/formaldehydecondensates. Known processes for preparing the aniline/formaldehydecondensates and the resultant polyisocyanates are described in theliterature and in many patents, for example, U.S. Pat. Nos. 2,683,730,2,950,263, 3,012,008, 3,344,162 and 3,362,979. The isocyanates usefulherein contain from about 40 to about 85% by weight of methylenebis(phenyl isocyanate) and have an isocyanate group content of fromabout 20 to about 35% by weight (preferably from about 30 to about 35%by weight and most preferably from about 31 to about 33% by weight). Asnoted above, the isocyanate index of the total system is from about 95to about 105.

Water is used in an amount ranging from about 2 to about 10 pads byweight per 100 pads by weight of component A).

The silicone surfactants, which can be used in amounts of from 0 toabout 1.0 pad by weight per 100 pads by weight of component A), areknown in the art. In fact, one advantage of the present invention isthat the surfactant is not even necessary. Polyether siloxanes areparticularly suitable silicone surfactants; especially useful are thosewhich are water soluble. These compounds generally have a polydimethylsiloxane group attached to a copolymer of ethylene oxide and propyleneoxide. Foam stabilizers of this kind are known and have been described,for example, in U.S. Pat. Nos. 2,834,748, 2,917,480 and 3,629,308. Alsouseful are the known polysiloxane surfactants generally used in thepolyurethane art.

The reaction mixture must also contain a catalyst in an amount of fromabout 0.05 to about 1.0 parts by weight per 100 parts by weight ofcomponent A). Catalysts which promote the reaction of water andisocyanate groups are known in the art. These catalysts are generallyknown and include tertiary amines such as triethylamine, tributylamine,N-methylmorpholine, N-ethylmorpholine, N-cocomorpholine,N,N,N',N"-tetramethyl-ethylene-diamine,1,4-diaza-bicyclo-(2,2,2)-octane, N-methyl-N'-dimethyl-amino-ethylpiperazine, N,N-dimethylbenzylamine, bis-(N,N-diethyl-aminoethyl)-adipate, N,N-diethylbenzylamine, pentamethyl-diethylenetriamine, N,N-dimethyl-cyclohexylamine, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-dimethyl-β-phenylethylamine1,2-dimethylimidazole, 2-methylimidazole and the like. Also useful arethe commercially available tertiary amines such as Niax Al and NiaxAl07, available from Union Carbide; Thancat DD, available from Texaco;and the like. Mannich bases known per se obtained from secondary aminessuch as dimethylamine and aldehydes, preferably formaldehyde, or ketonessuch as acetone, methyl ethyl ketone or cyclohexanone and phenols suchas phenol nonylphenol or bisphenol may also be used as catalysts.Silaamines having carbon-silicon bonds as described, e.g., in GermanPatent No. 1,229,290 and U.S. Pat. No. 3,620,984 may also be used ascatalysts. Examples include 2,2,4-trimethyl-2-silamorpholine and1,3-diethylaminoethyltetramethyldisoloxane.

According to the invention, the components may be reacted together byknown processes often using mechanical devices such as those describedin U.S. Pat. No. 2,764,565. Details concerning processing apparatuswhich may be used according to the invention may be found in KunststoffHandbuch, Volume VII, published by Vieweg and Hochtlen,Carl-Hanser-Verlag, Munich, 1966, pages 121 and 205.

The foaming reaction is carded out inside molds. In this process, thefoamable reaction mixture is introduced into a mold which may be made ofa metal such as aluminum or a plastics material such as an epoxideresin. The reaction mixture foams up inside the mold to produce theshaped product. The process of foaming in molds is carded out to producea product having a cellular structure. According to the invention, thedesired result can be obtained by introducing just sufficient foamablereaction mixture to fill the mold with foam after the reaction iscompleted.

So-called external mold release agents known in the art, such assilicone waxes and oils, are frequently used when foaming is carded outinside the molds. The process may also be carded out with the aid ofso-called internal mold release agents, if desired, in combination withexternal mold release agents. e.g., described in GermanOffenlegungsschriften Nos. 2,121,670 and 2,307,589.

The invention is further illustrated but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

EXAMPLES

In the examples which follow, the following materials were used:

a) Polyol A: a dispersion of a polyurea having an OH number of about 45and a solids content of about 28%, and commercially available asMultranol 9184 from Miles Inc.

b) Polyol B: a polyether prepared from propylene glycol, propylene oxideand ethylene oxide having an OH number of about 28 and a primaryhydroxyl group content of about 75%. The weight ratio of propylene oxideto ethylene oxide is about 6.7:1,

c) Polyol C: a monoethanolamine/propylene oxide adduct having amolecular weight of about 240 (OH number 700).

d) Amine: Jeffamine T-5000, a 5000 molecular weight polypropylene oxidetriamine, commercially available from Texaco.

e) Water

f) B8002: a commercially available silicon for cell stabilization andcell size regulation from Goldschmidt.

g) A1: Niax A1, a tertiary amine catalyst commercially available fromUnion Carbide.

h) Iso A: a polymethylene poly(phenyl isocyanate) containing about 45%by weight diisocyanate, having an isocyanate group content of about31.5%, an equivalent weight of about 133, and a viscosity of about 200mPa.s at 25° C., commercially available from Miles Inc.

i) Iso B: a polymethylene poly(phenyl isocyanate) containing about 59%by weight diisocyanate, having an isocyanate group content of about32.25%, an equivalent weight of about 131, and a viscosity of about 60mPa.s at 25° C., commercially-available from Miles Inc.

Examples 1 and 2

In Examples 1 and 2, the components of the B-side were accuratelyweighed into a suitable container and mixed using an air driven twoblade mixer. The resultant mixture was then taken to the meteringequipment. The metering equipment was flushed with the mixture andcalibrated for the desired foam index. The mixture was mixed with theisocyanate using high pressure metering equipment (Hennecke HK100) and aHennecke MQ-12-2 self-cleaning mixhead. Process settings were asfollows:

Temperature (B-side and isocyanate): 80° F. (27° C.)

Mix pressures (B-side and isocyanate): 2500 psi (17.5 N/mm²)

Mold temperature: 150° F. (66° C.)

Mold release: PRC 1189C from Chemtrend

Demold time: 3 minutes

The reaction mixture was metered into a 15 inch×15 inch×4 inch (25.4cm×25.4 cm×6.35 cm) mold (which had been previously sprayed with themold release), in an amount sufficient to give the desired foam density.The mold was then closed and the foam part demolded after the reactionwas complete (3 minutes).

The formulations used and the results obtained were as reported in Table1 (all amounts are in parts by weight). Testing was conducted inaccordance with Chrysler specification DC-640.

                  TABLE 1                                                         ______________________________________                                        Example         1       2                                                     ______________________________________                                        B-SIDE                                                                        Polyol A        35      35                                                    Polyol B        20      20                                                    Polyol C        35      35                                                    Amine           10      10                                                    Water           7       3.1                                                   B8002           0.25    0.25                                                  A1              0.3     0.3                                                   ISOCYANATE at 100 Index                                                       Iso A           x       x                                                     Density, kg/m.sup.3                                                                           3.38    5.32    ASTM-D-1622                                   Elongation, %   10.5    13.9    ASTM-D-3574                                   MVSS-302, mm/sec                                                                              0       0                                                     Volume change, %                ASTM-D-2126                                   2B, 28 days     0.85    0.19                                                  1D, 28 days     2.06    1.4                                                   1K, 28 days     0.73    0.05                                                  ______________________________________                                    

Examples 3 through 6

In Examples 3 through 6, the components of the B-side were accuratelyweighed into a suitable container and mixed. A sufficient amount ofisocyanate was then added to the mixture at an isocyanate index of 100and in an amount sufficient to give 175 grams of total reaction mixture,The mixture was intensively mixed for 10 seconds and the reactivities ofthe systems were observed. In each case, a foam system having a goodreaction profile was obtained. The formulations used were as reported inTable 2 (all amounts are in parts by weight).

                  TABLE 2                                                         ______________________________________                                        Example       3      4         5    6                                         ______________________________________                                        B-SIDE                                                                        Polyol A      40     30        40   30                                        Polyol C      50     60        50   60                                        Amine         10     10        10   10                                        Water         4      3.25      4    3.25                                      B8002         0.25   0.25      0.25 0.25                                      A1            0.3    0.3       0.3  0.3                                       ISOCYANATE                                                                    Iso A         x      x                                                        Iso B                          x    x                                         ______________________________________                                    

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. A water blown, energy absorbing foam produced byreacting:A) an isocyanate reactive mixture comprising;1) from about 25to about 50% by weight of filled polyol having an OH number of from 25to 50, 2) from 0 to about 30% by weight of a polyether diol having ahydroxyl functionality of 2 and having an OH number of from about 25 toabout 75, and wherein at least 75% of the hydroxyl groups are primaryhydroxyl groups, 3) from about 20 to about 70% by weight of an adduct ofa mono-, di-, or trialkanolamine and propylene oxide, said adduct havinga hydroxyl number of from about 100 to about 800, and 4) from about 5 toabout 20% by weight of a polyoxyalkylene polyamine having a molecularweight of from about 2000 to about 5000, and containing from 2 to 3primary amino groups,wherein the percents by weight are based upon thetotal weight of the isocyanate reactive mixture and .wherein thepercents by weight total 100%. B) a polymethylene poly(phenylisocyanate) containing from about 40 to about 85% by weight of methylenebis(phenyl isocyanate) and having an isocyanate group content of fromabout 30 to about 35% by weight, with the amount of said isocyanate B)being such that the isocyanate index of the mixture of all theisocyanate reactive components and said isocyanate is from about 95 toabout 105, and C) from about 2 to about 10 parts by weight per 100 partsby weight of component A) of water, in the presence of D) from 0 toabout 1 part by weight per 100 parts by weight of component A) of asilicone surfactant, E) from about 0.05 to about 1.0 part by weight per100 parts by weight of component A) of an amine compound which willcatalyze the reaction between water and an isocyanate group.
 2. The foamof claim 1, wherein said isocyanate has an isocyanate group content offrom about 30 to about 35% by weight.
 3. The foam of claim 1, whereinsaid filled polyol is a dispersion of a polyurea and/orPolyhydrazodicarbonamide in a relatively high molecular weight organiccompound containing at least two hydroxyl groups, wherein theconcentration of the polyurea and/or polyhydrazodicarbonamide is from 1to 40% by weight based upon 100 parts by weight of said organiccompound.
 4. The foam of claim 1, wherein component b) is present in anamount of from about 15 to about 30% by weight, and wherein component c)is present in an amount of from about 20 to about 55% by weight.